1. Technical Field
The present invention relates to a power management function for a monitor.
2. Discussion of Related Art
These days, monitors are equipped with a power management function standardized according to an accepted standard, i.e., the Display Power Management Standard (DPMS) of the Video Electronics Standards Association (VESA). If the computer is left idle, it signals the monitor to gradually reduce power consumption to a fraction of the normal consumption.
The computer signals the monitor to assume various DPMS states, including full on, standby, suspend and off. In the xe2x80x98onxe2x80x99 state, there are no power savings, in xe2x80x98standbyxe2x80x99 the power savings are minimal, in xe2x80x98suspendxe2x80x99 state, the power savings are substantial, and in the xe2x80x98offxe2x80x99 state, the power savings are maximum. VESA adapted guidelines from an advanced power management (APM) specification created by Microsoft and Intel that provides an environment for power management of laptop computers by the system BIOS, operating system or applications, as shown in FIG. 1, taken from the VESA DPMS Standard. For instance, the BIOS can define several states, as shown in FIG. 2, taken from the Intel/Microsoft APM Specification. Transitions between these APM states result in calls to the display controller of FIG. 1, which in turn provides the DPMS hardware signaling defined by the VESA standard, as shown in FIG. 4. FIG. 3 shows a typical VGA cable extending between a host computer""s display controller and a display monitor, with numerous individual signal lines within the standard VGA cable. Only three of those lines are shown labeled in FIG. 3, since those are the only ones relevant to the VESA DPMS standard, i.e., video, horizontal synchronization, and vertical synchronization. Although shown as single lines, as will be appreciated by those of skill in the art, these signals are actually carried out on more than one line each. The display controller causes these signal lines to assume different signaling states according to the table shown in FIG. 4, as defined by the VESA DPMS standard. For instance, energy savings for a 130 watt monitor would be a few watts (e.g., down to  less than 90W) at the xe2x80x98standbyxe2x80x99 level, a very significant number of watts at the xe2x80x98suspendxe2x80x99 level (e.g., down to 10W), and perhaps a hundred watts or more representing almost, or even a complete, power shutdown (e.g., down to 5W).
A problem with the VESA DPMS standard is that, depending on the individual setup, it can involve equipment from numerous different vendors, all of which must interface with each other in a way as to signal and recognize the various states and to actually execute the VESA DPMS states in a way that works properly. Unfortunately, there are often mismatches between implementations that do not take into account peculiarities of different vendors"" implementations. This can cause a computer user to become frustrated, because the DPMS standard is not working properly, and he is not sure whether it is the fault of the computer or the display. Many times, the user will wrongly conclude that it is the display that is the problem, when it is really the display controller in the host, or the operating system of the host itself. This can lead to unnecessary trouble-shooting and much annoyance.
According to a first aspect of the invention, a display power management method comprises the steps of monitoring at a monitor a signal indicative of user activity, and timing within said monitor, for so long as said signal indicates user inactivity, successive periods of user inactivity, for initiating a corresponding series of successive greater power saving states, each of which terminates to a normal power consuming state upon detection of resumption of user activity as indicated by said signal or equivalently by some other similar signal indicative of user activity.
According further to the first aspect of the invention, the step of monitoring comprises repeatedly sensing or detecting in a display for the absence of any one of a plurality of signals provided to the display from a host computer over a standard interface cable for signaling various display power management states, and the step of timing further comprises the steps of upon first detecting the absence of any one of said plurality of signals while in a normal operating state, commencing a timing procedure while continuing to detect for said absence of said any one of said plurality of signals, whereby after a number of timeout periods energy consumption of said display is reduced in a comparable number of energy-saving operating states, and returning to said normal operating state upon no longer detecting said absence of said any one of said plurality of signals.
According still further to the first aspect of the invention, the number of energy-saving operating states includes a standby state with minimal power savings, a suspend state with substantial power savings, and an off stage with maximum power savings.
Still further according to the first aspect of the invention, upon said first detecting the absence of said any one of said plurality of signals, transitioning after a standby timeout period from a normal operating state of said display to a standby operating state with minimal power savings starting a suspend timeout period upon transitioning to said standby operating state, transitioning after said suspend timeout period to a suspend operating state, starting an off timeout period upon transitioning to said suspend operating state, transitioning after said off timeout period to an off operating state.
According to a second aspect of the invention, a monitor having a controller for receiving standard signals from a host computer for displaying information with display hardware further comprises a detector for detecting absence of any one of a plurality of display power management signals among said standard signals from said host computer, and a timer for timing transitions to a plurality of energy-saving states subsequent to said detecting the absence of said any one of the plurality of display power management signals for providing state transition timeout signals, wherein said display hardware is responsive to said state transition timeout signals for transitioning to said plurality of energy-saving states.
In further accord with the second aspect of the invention, the monitor further comprises manual controls for user selection of timeout periods for said timing of said transitions to said plurality of energy saving states.
These and other objects, features and advantages of the present invention will become more apparent in light of the detailed description of a best mode embodiment thereof, as illustrated in the accompanying drawing.